The present invention relates to a spark plug with an, in particular ceramic, insulator body and a center electrode, wherein said center electrode is housed at least partially in a bore in said insulator body, said center electrode being sealed off from said insulator body—preferably exclusively—by at least one sealing ring surrounding said center electrode.
In the state of the art, spark plugs have highly varied configurations of center and base electrodes. As a rule, the center electrode is guided in a bore in an insulator and projects beyond this on the combustion-chamber side. The seal between the center electrode and the insulator body, which is also decisive for the longevity and compressive strength of the spark plugs among other things, is normally realized by introducing glass-like or other sealing compounds between the center electrode and the insulator body. It is important that the sealing compound creates a gas-tight connection.
This way of sealing known in the state of the art has the disadvantage that it is relatively costly to introduce the sealing compound between the center electrode and the insulator body such that the desired gas-tight seal is ensured.
A glass seal in the form of a ring made of presintered glass powder is known from U.S. Pat. No. 4,563,158. The ring is pushed onto the center electrode. Then the glass powder is melted during exposure to heat and simultaneously pushed into its final position.
If these spark plugs known today are used in internal combustion engines, such as e.g. high-powered engines with very high internal pressures in the combustion chamber, the problem often arises that the spark plugs do not permanently have the required compressive strength. This can result either in gas escaping or the center electrode being pushed out of the insulator body during the operation of the internal combustion engine or being expelled at high pressure, which can in turn pose a risk for people and the machine.